The present invention relates generally to a feedback mechanism for deep brain electrical stimulation methods and, more particularly, methods for treating conscious patients having impaired cognitive function.
Brain injuries which lead to impaired cognitive function remain the least explored area for active neurological intervention. Several clinical observations suggest that mechanisms of plasticity are available to the brain that might be harnessed for therapeutic advantage for treating cognitive disorders. A significant percentage, roughly 20%, of patients who suffer severe brain damage remain conscious with preserved capacity for memory, attention, intention, and awareness. In many cases, these patients fluctuate dramatically (e.g., the well-known case of Gary Dockery, the brain-injured police officer who xe2x80x9cwoke upxe2x80x9d and interacted with his family for nearly twenty-four hours after seven years of minimal responsivenessxe2x80x94Chicago Tribune Jan. 29, 1997 xe2x80x9cAfter Miracle Coma Patient Has Way to Goxe2x80x9d).
There has been a striking lack of therapeutic options for these patients, despite evidence of their capacity to further optimize their brain function; this capacity is evident in the spontaneous fluctuations of functional level in many patients and the induced functional changes in some patients following sensory stimulation or patient initiated behaviors. The significance of developing a therapeutic intervention for patients having impaired cognitive function, especially those who remain conscious with preserved capacity for memory, attention, intention, and awareness lies in both the devastating reduction in quality of life they suffer and the economic burden these patients place on the health care system. These costs include full-time care in nursing and chronic rehabilitation facilities. Moreover, head trauma accounts for the largest percentage of these patients and most patients having impaired function caused by head trauma are under 40 years of age. Such patients represent a disproportionate economic cost in terms of both the loss of their expected productivity and the attendant costs of very long-term full-time care based on their young age.
Vestibular stimulation has been shown to reverse cognitive impairments. Schiff, et al., xe2x80x9cDoes Vestibular Stimulation Activate Thalamocortical Mechanisms That Reintegrate Impaired Cortical Regions?,xe2x80x9d Proc. R. Soc. Land. B. 266:421-23 (1999). However, improved procedures for controlling such stimulation is needed.
The present invention is directed to overcoming this deficiency.
The present invention relates to a method for treating a conscious patient to improve cognitive function. The method includes selecting a conscious patient who may or may not have impaired cognitive function. Electrical stimulation is then applied to at least a portion of the patient""s subcortical structures involved in the generation and control of generalized efference copy signals under conditions effective to improve the patient""s cognitive function. Internally generated movement of the patient is then detected and, in response to such internally generated movement, application of electrical stimulation is controlled.
The present invention also relates to a method for improving coordination of function across cortical regions in a patient. The method includes applying electrical stimulation to two or more subdivisions of the subcortical structures integrated in the generation and control of generalized efference copy signals. The two or more subdivisions modulate separate cortical regions. Electrical stimulation is again followed by detection of internally generated movement of the patient and, in response, control of the electric stimulation.
Using the methods of the present invention, patients suffering from impaired cognitive function can have at least a portion of the function restored, thus improving their quality of life and reducing societal costs. As a method of deep brain stimulation the present invention has several specific advantages over empirical adjustment of frequency and intensity of the electrical stimulation alone by identifying a natural pulse sequence for patterning of the stimulation. The added utility of these feedback pulses is that they offer increased flexibility in terms of both identifying additional targets of stimulation by using a synchronizing pulse that these areas are prepared to receive and improving the probability that complex brain injuries may be successfully treated because of a greater selectivity of using a natural pulse sequence. An important additional therapeutic advantage is that feedback as used here allows for patient biofeedback and self-regulation to play a role in the use of the application of the simulation technology for therapeutic purposes.